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Data Summary

Rapidly retreating thick ice fronts can generate large amounts of melange
(floating ice debris), which may affect episodes of rapid retreat of
Antarctic marine ice. In modern Greenland fjords, melange provides substantial
back pressure on calving ice faces, which slows ice-front calving rates.
On the much larger scales of West Antarctica, it is unknown if melange could
clog seaways and provide enough back pressure to act as a negative feedback
slowing retreat. Here we describe a new melange model, using a continuum
mechanical formulation that is computationally feasible for long-term
continental Antarctic applications. It is tested in an idealized rectangular
channel, and calibrated very basically using observed modern conditions in
Jakobshavn fjord, West Greenland. The model is then applied to drastic retreat
of Antarctic ice in response to warm mid-Pliocene climate. With melange
parameter values that yield reasonable modern Jakobshavn results, Antarctic
marine ice still retreats drastically in the Pliocene simulations, with little
slowdown despite the huge amounts of melange generated. This holds both for
the rapid early collapse of West Antarctica, and later retreat into major East
Antarctic basins. If parameter values are changed to make the melange much
more resistive to flow, far outside the range for reasonable Jakobshavn
results, West Antarctica still collapses and retreat is slowed or prevented
only in a few East Antarctic basins.